This project provides physical measurements of solar ultraviolet radiation (UVB) and epidemiological data and analyses relevant to the etiology of skin cancer, including malignant melanoma. Results from these studies supply scientific evidence related to the potential consequences of continued ozone depletion and climate change (i.e., global warming), and thus may be of use in developing policy relative to man-made atmospheric pollutants and international agreements to ban their use, such as the Montreal Protocol. Despite global predictions of stratospheric ozone depletion, our surface-based measurements of solar radiation of 290 nm to 330 nm wavelengths (UVB) continue to show no increasing trends. In addition to eight urban locations in the United States, similar UVB trends were found at two foreign stations and at rural locations, presumably free from industrial air pollution. Current analyses of epidemiologic data suggest that lifestyle patterns of sunlight exposure and not stratospheric ozone depletion are responsible for recent worldwide increases in the incidence of melanoma and skin cancer. Skin melanoma mortality rates were found to peak for individuals born during the 1950s, while trends in melanoma risk appeared to decline among younger cohorts and age groups under 30. Without additional increases in UVB exposure, we predict that skin melanoma age-adjusted mortality rates will decline in about 20 years.